1. Field of the Invention
The present invention relates to a backplate for a Plasma Display Panel (PDP) and a method for fabricating thereof, and in particular to a backplate for a PDP and a fabrication method thereof which are capable of uniformly coating a phosphor material on an inner portion (a region of a backplate and a region surrounded by the barrier ribs) of a discharge cell of a PDP based on the height of a barrier rib.
2. Description of the Background Art
Recently, since the structure of a Plasma display Panel (PDP) is simple as a flat type display unit and there is not limit in the size of the display, the PDP will receive a big attention as a key display unit in the flat display market. In the PDP, ultraviolet rays generated during a plasma discharge by Hexe2x80x94Ne or Nexe2x80x94Xe gas in discharge cells separated by the barrier ribs excite Red, Green and Blue phosphor materials formed on the barrier ribs, so that a visual ray is generated when the excited phosphor material is transited to a base state. Therefore, a certain character or graphic is displayed by the thusly emitted visual rays using the above-described visual ray discharge principle.
FIG. 1 is a view illustrating the structure of an AC-PDP and one cell in a conventional AC-PDP which includes a front glass substrate 1 for displaying an age, a backplate 23 installed parallel with the front glass substrate 1 and distanced from the front glass substrate 1 by a certain distance, and a plurality of barrier ribs 13 formed between the front glass substrate 10 and the backplate 12 a certain distance therebetween for forming a discharge region in the interior of a discharge cell for preventing an electrical/optical interference between the cells.
Here, the front glass substrate 1 includes an upper dielectric layer 3 for cumulating a barrier wall electric charge, sustaining a discharge sustaining voltage, protecting electrodes from an ion impact during a gas discharge and preventing diffusion of ions, and a protection film layer 9 formed on the surface of the upper dielectric layer 3, protecting the upper dielectric layer 3 from a sputtered plasma particle, extending the life span of the same, increasing the efficiency of the discharge of a relatively high secondary electron when a relatively low ion energy collides with the surface during the plasma discharge and decreasing the changes of a discharge characteristic of a fireproof metal. At this time, the protection film layer 9 is formed of MgO.
In the interior of the upper dielectric layer 3, there are a sustain electrode 5 using Indium tin Oxide (ITO) as a transparent electrode, and a bus electrode 7 formed of a metal engaged with the sustain electrode 5.
The backplate 23 includes an address electrode 19 for generating a discharge with respect to the sustain electrode 5 and the bus electrode 7, an under layer 21 for adhering the address electrode 19 and the backplate, a lower dielectric layer 17 for covering the address electrode 19, and a phosphor material 15 for covering the lower dielectric layer 17 and the barrier ribs 13 formed thereon and generating a visual ray.
A black top 11 is engaged at an upper end of the barrier rib 13 for absorbing light externally inputted through the front glass substrate 1.
In the thusly constituted PDP, in a state that a mixed gas of Hexe2x80x94Ne and Nexe2x80x94Xe is filled, a discharge is generated between the address electrode 19 and the sustain electrode 5, and when a discharge is continuously generated between the sustain electrodes 5, a vacuum ultraviolet (VUV) of 147 nm wavelength is outputted. Thereafter, the vacuum ultraviolet ray excites the phosphor material 15. When the phosphor material is transited from the excited state to the base state, a visual ray of Red, Green and Blue is discharged, so that a certain image is displayed on the front glass substrate 1.
Therefore, since the phosphor material 15 outputs light for displaying a certain image on the front glass substrate, the phosphor material 15 must be uniformly coated at the discharge cell based on a material characteristic of the phosphor material.
As a method for coating the phosphor material, there are a screen printing method, a sand blast method, a photolithography method, an electric melting method, etc. Among the above-described methods, the screen printing and sand blast methods are widely used.
FIG. 2 is a flow chart of a fabrication method of a backplate of a conventional PDP using a screen printing method. As shown therein, a screen mask is arranged on the backplate having barrier ribs. The above-described fabrication method includes a step ST11 for arranging a screen mask on the backplate for coating a red phosphor material, and a step ST12 for printing/drying the red phosphor material for thereby coating a red phosphor material. Identically to the step for coating the red phosphor, material on the backplate, the screen mask is arranged on the backplate with respect to the green and blue phosphor materials in Steps ST13 and ST15. Thereafter, the green phosphor material and blue phosphor material are printed and dried in Step ST14 and ST16. The green and blue phosphor materials are sequentially coated on each discharge cell after coating the red phosphor material.
FIGS. 3A through 3C are cross-sectional views for coating a phosphor material on the discharge cell of the conventional PDP using the screen printing method.
As shown in FIG. 3A, the screen mask 33 is positioned on the backplate 23 on which the under layer 21, the address electrode 19, the lower dielectric layer 17 and the barrier ribs 13 are sequentially formed, and the red, green or blue phosphor material 15 of the paste state is printed on the backplate 23. After printing the phosphor material, the screen mask 33 is removed, and as shown in FIG. 3B, the phosphor material 15 is coated a height similar to the height of the barrier rib 13. At this time, when drying the backplate including the coated phosphor material, as shown in FIG. 3C, an organic solvent is evaporated, and the volume of the same is decreased. Therefore, the phosphor material 15 is coated only on the surfaces of the lower dielectric layer 17 and the barrier ribs 13.
FIG. 4 is a flow chart of a backplate fabrication method of a conventional PDP using the sand blast method. As shown therein, the method includes Steps ST21, ST23 and ST25 for printing and drying the red, green and blue phosphor materials on the front surface of the backplate 23 having the barrier ribs, Steps ST22, ST24 and ST26 for light-exposing and developing the red, green and blue phosphor materials using a desired screen mask, so that the red, green and blue phosphor materials are coated on a corresponding discharge cell at the height of the barrier ribs. Next, glass bids are sprayed for thereby partially removing the red, green and blue phosphor materials, so that the red, green and blue phosphor materials are coated on the surfaces of the lower dielectric layer 17 and the barrier ribs 13 in Step ST27. Next, the backplate coated with the phosphor materials is molded for thereby forming the red, green and blue phosphor materials in Step ST28.
In the conventional screen printing method or sand blast method, in the case that the height of the barrier rib 13 is 100xcx9c200 xcexcm, it is possible to coat the phosphor material at the height of the entire barrier ribs.
However, in order to increase the discharge efficiency, the PDP using the high frequency discharge must have an enough distance between two electrodes which generate a high frequency discharge. Therefore, the height of the barrier ribs is generally 500xcx9c2000 xcexcm. In the case that the height of the barrier rib is high, it is impossible to uniformly coat the phosphor material by the conventional screen printing method and sand blast method. Namely, since the barrier ribs having the coated phosphor materials is formed of a glass having a high friction coefficient or a glass-ceramic material, when printing the paste state phosphor material, the paste state phosphor material does not flow into a deep portion, so that an uniform coating is not implemented.
Therefore, if the thickness of the coated phosphor material layer is non-uniform, the reflection of the visual light outputted from every discharge cell is non-uniform for thereby causing a certain image distortion. In particular, it is difficult to uniformly coat the phosphor with respect to the high frequency PDP of a lattice structure formed of the discharge cells having a high height of the barrier rib in order to prevent any optical interference between discharge cells. In addition, it is difficult to accurately adjust the position of the screen mask for coating red, green and blue phosphor materials on a corresponding cell.
Accordingly, it is an object of the present invention to provide a PDP(Plasma Display Panel) capable of uniformly coating a phosphor material on a backplate having a plurality of barrier ribs irrespective of the shape and height.
It is another object of the present invention to provide a back glass fabrication method for a PDP capable of uniformly coating a phosphor material on a backplate having a plurality of barrier ribs irrespective of the shape and height.
It is another object of the present invention to provide a PDP capable of coating a lubricant thin film on a backplate having a plurality of barrier ribs irrespective of the shape and height and uniformly coating a phosphor material on a backplate having a coated lubricant thin film.
It is another object of the present invention to provide a PDP fabrication method capable of coating a lubricant thin film on a backplate having a plurality of barrier ribs irrespective of the shape and height and uniformly coating a phosphor material on a backplate having a coated lubricant thin film.
It is another object of the present invention to provide a PDP capable of uniformly coating a phosphor material on a backplate having a height higher than 500 xcexcm and a plurality of barrier ribs irrespective of shape.
It is another object of the present invention to provide a backplate fabrication method for a PDP capable of uniformly coating a phosphor material on a backplate having a height higher than 500 xcexcm and a plurality of barrier ribs irrespective of shape.
To achieve the above objects, there is provided a backplate of a Plasma Display Panel (PDP) which includes a lubricant thin film layer formed on a front surface of a backplate having a barrier rib, and a phosphor material layer formed on the lubricant thin film layer.
To achieve the above objects, there is provided a backplate fabrication method for a PDP which includes a step for coating a lubricant material on a substrate having a barrier rib and forming a lubricant thin film, and a step for coating a phosphor material on the lubricant thin film.
To achieve the above objects, there is provided a backplate fabrication method for a PDP which includes the steps of coating a photosensitive phosphor material on a front surface of a backplate having a barrier rid, spraying a compression gas so that the photosensitive phosphor material is uniformly coated on a bottom portion of the backplate in which the barrier ribs are formed, and light-exposing/developing and drying the regions which will be coated with the phosphor material.